As reported by the University of Florida Plant Pathology Department, fungal and bacterial pathogens can lower yields, reduce quality, negatively affect the aesthetic and economic value and even ultimately destroy plants, crops, pre-harvest fruits, trees, vegetables and grasses. In particular, bacterial and fungal diseases in citrus plants create huge economic burdens on the citrus industry worldwide. Citrus canker alone causes severe economic consequences in the world's citrus growing regions. The bacteria which causes citrus canker, Xanthomonas campestris pv. citri, has been found in southern Asia, Japan, the Middle East, Africa, South America and now North America. Historically, citrus canker outbreaks have occurred in North America in the early 1900s and again in 1986. Fortunately, through the use of aggressive eradication techniques, the disease was eliminated in both instances. Citrus canker, however, can be reintroduced when people inadvertantly transport infected citrus fruits and seedlings into citrus growing areas in the U.S. and elsewhere. In the U.S., Florida is by far the state most at risk from citrus canker given its combination of high humidity throughout the year, seasonal hurricanes and frequent thunderstorms accompanied by high wind gusts. (See The University of Florida Plant Pathology Department Report at www.biotech.ufl.edu/PlantContainment/canker.htm)
The University of Florida Extension Service reports that in 1995 citrus canker was again detected in the U.S. in citrus trees in the Miami-Dade County, Florida area. Citrus canker then spread to the commercial groves in southwest Florida. Since 1998 more than 870,000 trees have been destroyed in conjunction with-eradication programs. (See http://edis.ifas.ufl.edu/FE286)
Costs in managing the threat of citrus canker include capital investment for spray equipment, the lost value of affected fruit, costs associated with inspection and eradication, and costs associated with the creation of natural windbreaks and other defensive tactics. Current spraying programs include relatively expensive copper based sprays. The University of Florida Extension Service has estimated that if citrus canker became endemic in Florida, the total cost for countering endemic citrus canker, including the use of copper based sprays, could be more than $300 per acre.
Many types of organic molecules possess antimicrobial properties and can be used to effectively control fungal and bacterial disease in plants. However, many of the currently used pesticides are toxic to humans, animals and the exposed environment which limits large scale application in, for example, citrus orchards. The Environmental Protection Act was established in 1972, in part, to address concerns over the use of potentially toxic materials to control or treat diseases in crops. In 1996 Congress passed the Food Quality Protection Act requiring the Environmental Protection Agency to reassess the safety and efficacy of every existing pesticide by 2006. Concerns about pesticide residues on plants and the exposure of field workers to such residues severely limits the amounts of pesticide that can be applied and the timing of such application. These limitations decrease the potential effectiveness of commonly used pesticides to prevent and treat bacterial and fungal disease in plants in general and citrus canker in particular.
Accordingly, there exists a tremendous need for effective, economical and non-toxic compositions and methods for preventing and treating bacterial and fungal disease in plants. In particular there is a tremendous need for effective, economical and non-toxic compositions and methods for preventing and treating citrus canker.